In a hybrid resin-sealed semiconductor device having a plurality of hybrid resin-sealed semiconductor elements, heat generated from the semiconductor elements must be effectively radiated. For this reason, the semiconductor elements must be arranged on a heat sink.
In the above resin-sealed semiconductor device, each semiconductor element constitutes an independent circuit in a package. For this reason, the elements, more specifically, collectors formed on the bottom surfaces of transistors must be insulated from each other. Therefore, the following arrangement is employed.
In FIG. 3, semiconductor elements 33a and 33b are formed on the heat sinks 31a and 31b through semiconductor pastes 32a and 32b, respectively, and wires 34a to 34d connected to inner leads (not shown) are bonded to predetermined portions of the heat sinks 31a and 31b and the semiconductor elements 33a and 33b, respectively.
With the above arrangement, since the heat sinks 31a and 31b are perfectly separated from each other, connection strength between a lead frame (not shown) and the heat sinks 31a and 31b is weakened. Therefore, after the wires 34a to 34d are bonded, the wires are probably disconnected by vibration in other manufacturing steps. This is a disadvantageous problem in the manufacture.
In FIG. 4, a conductive paste 42 and a ceramic plate 43 are formed on a heat sink 41, and a conductive material on the ceramic plate 43 is patterned to form inner leads 44a and 44b. Semiconductor elements 46a and 46b are formed on the inner leads 44a and 44b through conductive pastes 45a and 45b, respectively, and wires 47a to 47d are bonded to predetermined portions of the semiconductor elements 46a and 46b and inner leads 44a and 44b, respectively.
With the above arrangement, since a special-purpose device for arranging the ceramic plate 43 on the heat sink 41 must be used, the semiconductor device cannot be manufactured in a production line of a general-purpose semiconductor device. Therefore, a production cost is largely increased, and the unit cost of the semiconductor device is increased. In addition, the thin ceramic plate having a large area is easily cracked, and it cannot be easily treated.
In FIG. 5, inner leads 52a and 52b are arranged to be separated from a heat sink 51, and semiconductor elements 54a and 54b are formed on the inner leads 52a and 52b through conductive pastes 53a and 53b, respectively. Wires 55a and 55b are bonded to predetermined portions of the semiconductor elements 54a and 54b, respectively.
With the above arrangement, the inner leads 52a and 52b cannot easily be processed. In addition, in order to obtain effective heat radiation, the inner leads 52a and 52b having the semiconductor elements 54a and 54b must be formed as close to the heat sink 51 as possible, and the inner leads 52a and 52b and the heat sink 51 must be assembled with strict accuracy. This accuracy largely influences heat-radiation characteristics of the semiconductor device, i.e., the characteristics of the semiconductor device and causes the product yield of the semiconductor to decrease. Therefore, the semiconductor device cannot be manufactured in mass production.
In FIGS. 3 to 5, although the conductive pastes 32a, 32b, 42, 45a, 45b, 53a, and 53b are used, soldering may be used in place of the conductive pastes.
It is an object of the present invention to provide a resin-sealed semiconductor device capable of reliably insulating semiconductor elements from each other, effectively radiating heat generated from the semiconductor elements, and reducing a manufacturing cost to be low.